Yes, and conjure candles are reusable too 🙌 Since you're petitioning directly to the spirits, you can ask for both people to be brought to you. It isn't like a spelled candle where there is a limited amount of energy.
you could do two separate rituals, one for each person, but you might as well just name the second person in the ritual cause the spirits are already there and listening.
For which planet? There are multiple 4th pentacles.